A radio spectrum resource is a scarce strategic resource, and a regulatory body in each country has strict specifications on use of the radio spectrum resource. Currently, a common practice is dividing a radio spectrum into licensed bands and unlicensed bands by means of fixed allocation and designation. Most radio spectra are licensed bands and exclusively used by particular systems, for example, broadcast television bands and business mobile communication bands. Some spectra, for public service and welfare purposes such as industry, scientific research, and medical purposes, are open to the public for free as unlicensed resources, for example, wireless intercom, Wireless Fidelity (“Wi-Fi”), and Bluetooth.
As the wireless communications industry is expanding sharply, a contradiction between spectrum demand and spectrum supply is increasingly prominent, and licensed bands alone cannot meet demands for future mobile broadband (“MBB”) development and experience. To obtain more spectrum resources, the wireless communications industry organization (the 3rd Generation Partner Project (“3GPP”) turns eyes on unlicensed bands, expecting to use the unlicensed bands as a beneficial supplementation to the licensed bands.
However, unlicensed bands to be focused in deployment by the industry, such as a low-frequency band 5 GHz and a high-frequency band 60 GHz, already exist or are to be deployed for other unlicensed systems. Wi-Fi is a typical representative therein. On the 5 GHz frequency band, an 802.11a/n/ac system is deployed. On the 60 GHz frequency band, an 802.11ad system is deployed. Therefore, a 3GPP system needs to contend with these systems for use of spectrum resources on the unlicensed bands. This fact leads to a result that the 3GPP system needs to share the resources with another system on the unlicensed bands, thereby causing the 3GPP system to be in a state of opportunity-based and discontinuous transmission on the unlicensed bands, and a start location of each resource segment to be unfixed. This results from random contention.
A 3GPP system uses base-station-centered centralized network control (network-centric), so when the 3GPP system performs opportunity-based contention with another system for resources, a base station represents an entire network to contend with a device in the another system for permission to use the resources. After obtaining the resources by means of contention, the base station needs to notify a terminal device of a result of the contention. When the base station is in a state of opportunity-based and discontinuous information transmission on a band, to ensure that the terminal device can successfully receive information sent by the base station on the band, a method used in a current technology is to keep the terminal device in an information receiving state on the band all the time, however, bringing unnecessary power consumption overheads.
Therefore, when a wireless access device is in a state of opportunity-based and discontinuous information transmission on a band, how to reduce power consumption overheads of a terminal device is an urgent problem to be resolved currently.